Moonlighting activity of presenilin in plants is independent of gamma-secretase and evolutionarily conserved.
Ontology highlight
ABSTRACT:
SUBMITTER: Khandelwal A
PROVIDER: S-EPMC1948938 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:In neuronal cells, presenilin-dependent gamma-secretase activity cleaves amyloid precursor proteins to release Abeta peptides, and also catalyzes the release of the intracellular domain of the transmembrane receptor Notch. Accumulation of aberrant Abeta peptides appears to be causally related to Alzheimer's disease. Inhibition of Abeta peptide production is therefore a potential target for therapeutic intervention. Notch proteins play an important role in cell fate determination in many different organisms and at different stages of development, for example in mammalian T cell development. We therefore addressed whether structurally diverse gamma-secretase inhibitors impair Notch function by studying thymocyte development in murine fetal thymic organ cultures. Here we show that high concentrations of the most potent inhibitors blocked thymocyte development at the most immature stage. In contrast, lower concentrations or less potent inhibitors impaired differentiation at a later stage, most notably suppressing the development of CD8 single-positive T cells. These phenotypes are consistent with an impairment of Notch signaling by gamma-secretase inhibitors and define a strict Notch dose dependence of consecutive stages during thymocyte development.
| S-EPMC55417 | biostudies-literature
Project description:Presenilin (PS), a causative molecule of familial Alzheimer disease, acts as a crucial component of the ?-secretase complex, which is required to cleave type I transmembrane proteins such as amyloid precursor protein and Notch. However, it also functions through ?-secretase-independent pathways. Recent reports suggested that PS could regulate the expression level of cell surface receptors, including the PDGF and EGF receptors, followed by modulating their downstream pathways via ?-secretase-independent mechanisms. The main purpose of this study was to clarify the effect of PS on expression of the insulin receptor (IR) as well as on insulin signaling. Here, we demonstrate that PS inhibited IR transcription and reduced IR expression, and this was followed by down-regulation of insulin signaling. Moreover, we suggest that neither ?-secretase activity nor Wnt/?-catenin signaling can reduce the expression of IR, but a PS-mediated increase in the intracellular Ca(2+) level can be associated with it. These results clearly indicate that PS can functionally regulate insulin signaling by controlling IR expression.
| S-EPMC3137102 | biostudies-literature
Project description:A complex composed of presenilin (PS), nicastrin, PEN-2, and APH-1 is absolutely required for ?-secretase activity in vivo. Evidence has emerged to suggest a role for PS as the catalytic subunit of ?-secretase, but it has not been established that PS is catalytically active in the absence of associated subunits. We now report that bacterially synthesized, recombinant PS (rPS) reconstituted into liposomes exhibits ?-secretase activity. Moreover, an rPS mutant that lacks a catalytic aspartate residue neither exhibits reconstituted ?-secretase activity nor interacts with a transition-state ?-secretase inhibitor. Importantly, we demonstrate that rPS harboring mutations that cause early onset familial Alzheimer's disease (FAD) lead to elevations in the ratio of A?42 to A?40 peptides produced from a wild-type APP substrate and that rPS enhances the A?42/A?40 peptide ratio from FAD-linked mutant APP substrates, findings that are entirely consistent with the results obtained in in vivo settings. Thus, ?-secretase cleavage specificity is an inherent property of the polypeptide. Finally, we demonstrate that PEN2 is sufficient to promote the endoproteolysis of PS1 to generate the active form of ?-secretase. Thus, we conclusively establish that activated PS is catalytically competent and the bimolecular interaction of PS1 and PEN2 can convert the PS1 zymogen to an active protease.
| S-EPMC3003001 | biostudies-literature
Project description:Presenilin is the catalytic subunit of γ-secretase, a four-component intramembrane protease responsible for the generation of β-amyloid (Aβ) peptides. Over 200 Alzheimer's disease-related mutations have been identified in presenilin 1 (PS1) and PS2. Here, we report that Bax-inhibitor 1 (BI1), an evolutionarily conserved transmembrane protein, stably associates with PS1. BI1 specifically interacts with PS1 in isolation, but not with PS1 in the context of an assembled γ-secretase. The PS1-BI1 complex exhibits no apparent proteolytic activity, as judged by the inability to produce Aβ40 and Aβ42 from the substrate APP-C99. At an equimolar concentration, BI1 has no impact on the proteolytic activity of γ-secretase; at a 200-fold molar excess, BI1 reduces γ-secretase activity nearly by half. Our biochemical study identified BI1 as a PS1-interacting protein, suggesting additional functions of PS1 beyond its involvement in γ-secretase.
| S-EPMC6320538 | biostudies-literature
Project description:Presenilin is the catalytic component of the γ-secretase complex, a membrane-embedded aspartyl protease that plays a central role in biology and in the pathogenesis of Alzheimer's disease. Upon assembly with its three protein cofactors (nicastrin, Aph-1 and Pen-2), presenilin undergoes autoproteolysis into two subunits, each of which contributes one of the catalytic aspartates to the active site. A family of presenilin homologs, including signal peptide peptidase, possess proteolytic activity without the need for other protein factors, and these simpler intramembrane aspartyl proteases have given insight into the action of presenilin within the γ-secretase complex. Cellular and molecular studies support a nine-transmembrane topology for presenilins and their homologs, and small-molecule inhibitors and cysteine scanning with crosslinking have suggested certain presenilin residues and regions that contribute to substrate recognition and handling. Identification of partial complexes has also offered clues to protein-protein interactions within the γ-secretase complex. Biophysical methods have allowed 3D views of the γ-secretase complex and presenilins. Most recently, the crystal structure of a microbial presenilin homolog has confirmed a nine-transmembrane topology and intramembranous location and proximity of the two conserved and essential aspartates. The crystal structure also provides a platform for the formulation of specific hypotheses regarding substrate interaction and catalysis as well as the pathogenic mechanism of Alzheimer-causing presenilin mutations. This article is part of a Special Issue entitled: Intramembrane Proteases.
| S-EPMC3801419 | biostudies-literature
Project description:Presenilin heterodimers apparently contain the active site of gamma-secretase, a polytopic aspartyl protease involved in the transmembrane processing of both the Notch receptor and the amyloid-beta precursor protein. Although critical to embryonic development and the pathogenesis of Alzheimer's disease, this protease is difficult to characterize, primarily because it is a multicomponent complex of integral membrane proteins. Here the functional gamma-secretase complex was isolated by using an immobilized active site-directed inhibitor of the protease. Presenilin heterodimers and nicastrin bound specifically to this inhibitor under conditions tightly correlating with protease activity, whereas several other presenilin-interacting proteins (beta-catenin, calsenilin, and presenilin-associated protein) did not bind. Moreover, anti-nicastrin antibodies immunoprecipitated gamma-secretase activity from detergent-solubilized microsomes. Unexpectedly, C83, the major endogenous amyloid-beta precursor protein substrate of gamma-secretase, was also quantitatively associated with the complex. These results provide direct biochemical evidence that nicastrin is a member of the active gamma-secretase complex, indicate that beta-catenin, calsenilin, and presenilin-associated protein are not required for gamma activity, and suggest an unprecedented mechanism of substrate-protease interaction.
| S-EPMC122414 | biostudies-literature
Project description:Neurexins are a large family of neuronal plasma membrane proteins, which function as trans-synaptic receptors during synaptic differentiation. The binding of presynaptic neurexins to postsynaptic partners, such as neuroligins, has been proposed to participate in a signaling pathway that regulates synapse formation/stabilization. The identification of mutations in neurexin genes associated with autism and mental retardation suggests that dysfunction of neurexins may underlie synaptic defects associated with brain disorders. However, the mechanisms that regulate neurexin function at synapses are still unclear. Here, we show that neurexins are proteolytically processed by presenilins (PS), the catalytic components of the γ-secretase complex that mediates the intramembraneous cleavage of several type I membrane proteins. Inhibition of PS/γ-secretase by using pharmacological and genetic approaches induces a drastic accumulation of neurexin C-terminal fragments (CTFs) in cultured rat hippocampal neurons and mouse brain. Neurexin-CTFs accumulate mainly at the presynaptic terminals of PS conditional double knockout (PS cDKO) mice lacking both PS genes in glutamatergic neurons of the forebrain. The fact that loss of PS function enhances neurexin accumulation at glutamatergic terminals mediated by neuroligin-1 suggests that PS regulate the processing of neurexins at glutamatergic synapses. Interestingly, presenilin 1 (PS1) is recruited to glutamatergic terminals mediated by neuroligin-1, thus concentrating PS1 at terminals containing β-neurexins. Furthermore, familial Alzheimer's disease (FAD)-linked PS1 mutations differentially affect β-neurexin-1 processing. Expression of PS1 M146L and PS1 H163R mutants in PS-/- cells rescues the processing of β-neurexin-1, whereas PS1 C410Y and PS1 ΔE9 fail to rescue the processing defect. These results suggest that PS regulate the synaptic function and processing of neurexins at glutamatergic synapses, and that impaired neurexin processing by PS may play a role in FAD.
| S-EPMC3084856 | biostudies-literature
Project description:Severe early-onset familial Alzheimer's disease (FAD) is caused by more than 200 different mutations in the genes coding for presenilin, the catalytic subunit of the 4-subunit protease complex γ-secretase, which cleaves the C99 fragment of the amyloid precursor protein (APP) to produce Aβ peptides. γ-Secretase exists with either of two homologues, PS1 and PS2. All cryo-electron microscopic structures and computational work has so far focused on γ-secretase with PS1, yet PS2 mutations also cause FAD. A central question is thus whether there are structural and dynamic differences between PS1 and PS2. To address this question, we use the cryo-electron microscopic data for PS1 to develop the first structural and dynamic model of PS2-γ-secretase in the catalytically relevant mature membrane-bound state at ambient temperature, equilibrated by three independent 500 ns molecular dynamics simulations. We find that the characteristic nicastrin extra-cellular domain breathing mode and major movements in the cytosolic loop between TM6 and TM7 occur in both PS2- and PS1-γ-secretase. The overall structures and conformational states are similar, suggesting similar catalytic activities. However, at the sequence level, charge-controlled membrane-anchoring is extracellular for PS1 and intracellular for PS2, which suggests different subcellular locations. The tilt angles of the TM2, TM6, TM7 and TM9 helices differ in the two forms of γ-secretase, suggesting that the two proteins have somewhat different substrate processing and channel sizes. Our MD simulations consistently indicated that PS2 retains several water molecules near the catalytic site at the bilayer, as required for catalysis. The possible reasons for the differences of PS1 and PS2 are discussed in relation to their location and function.
| S-EPMC9065803 | biostudies-literature
Project description:gamma-Secretase is known to play a pivotal role in the pathogenesis of Alzheimer disease through production of amyloidogenic Abeta42 peptides. Early onset familial Alzheimer disease mutations in presenilin (PS), the catalytic core of gamma-secretase, invariably increase the Abeta42:Abeta40 ratio. However, the mechanism by which these mutations affect gamma-secretase complex formation and cleavage specificity is poorly understood. We show that our in vitro assay system recapitulates the effect of PS1 mutations on the Abeta42:Abeta40 ratio observed in cell and animal models. We have developed a series of small molecule affinity probes that allow us to characterize active gamma-secretase complexes. Furthermore we reveal that the equilibrium of PS1- and PS2-containing active complexes is dynamic and altered by overexpression of Pen2 or PS1 mutants and that formation of PS2 complexes is positively correlated with increased Abeta42:Abeta40 ratios. These data suggest that perturbations to gamma-secretase complex equilibrium can have a profound effect on enzyme activity and that increased PS2 complexes along with mutated PS1 complexes contribute to an increased Abeta42:Abeta40 ratio.
| S-EPMC2631949 | biostudies-literature
Project description:Mutations in the γ-secretase complex are strongly associated with familial Alzheimer disease. Both proteolytic and non-proteolytic functions for the γ-secretase complex have been previously described in mammalian model organisms, but their relative contributions to disease pathology remain unclear. Here, we dissect the roles of orthologs of the γ-secretase components in the model system Dictyostelium, focusing on endocytosis, lysosomal activity and autophagy. In this model, we show that the orthologs of PSEN (psenA and psenB), Ncstn (nicastrin) and Aph-1 (gamma-secretase subunit Aph-1), are necessary for optimal fluid-phase uptake by macropinocytosis and in multicellular development under basic pH conditions. Disruption of either psenA/B or Aph-1 proteins also leads to disrupted phagosomal proteolysis as well as decreased autophagosomal acidification and autophagic flux. This indicates a general defect in lysosomal trafficking and degradation, which we show leads to the accumulation of ubiquitinated protein aggregates in cells lacking psenA/B and Aph-1 proteins. Importantly, we find that all the endocytic defects observed in Dictyostelium PSEN ortholog mutants can be fully rescued by proteolytically inactive Dictyostelium psenB and human PSEN1 proteins. Our data therefore demonstrates an evolutionarily conserved non-proteolytic role for presenilin, and γ-secretase component orthologs, in maintaining Dictyostelium lysosomal trafficking and autophagy. Abbreviations: Atg8: autophagy protein 8a; Aph-1: gamma-secretase subunit Aph-1; crtA: calreticulin; ER: endoplasmic reticulum; GFP: green fluorescent protein; GSK3B: glycogen synthase kinase 3 beta; Ncstn: nicastrin; PSEN1: presenilin 1; psenA and psenB: Dictyostelium presenilin A and B; TRITC; tetramethylrhodamine isothiocyanate.
| S-EPMC6613883 | biostudies-literature